Welcome to HVAC-Talk.com, a non-DIY site and the ultimate Source for HVAC Information & Knowledge Sharing for the industry professional! Here you can join over 150,000 HVAC Professionals & enthusiasts from around the world discussing all things related to HVAC/R. You are currently viewing as a NON-REGISTERED guest which gives you limited access to view discussions

To gain full access to our forums you must register; for a free account. As a registered Guest you will be able to:

Participate in over 40 different forums and search/browse from nearly 3 million posts.

Want to install a split system in a house that already has forced hot air. Because the duct system is already installed, how would the return work? When I bought this house it never had A/C before,It is 1850 sq feet with 2 equal floors. I would like to use the existing ductwork as much as possible. Service tech suggested probably 4 ton. Any suggestions would be appreceated. Subject of return never came up. Thanks

I don't understand the focus on the return. Why isn't there a concern (or at least consideration) of all the ducts? The return is typically the best place to start because upgrading it will give you the biggest bang for the buck. But the supply ducts are important too.

In fact, if you don't address the upstairs supply ducts I can almost guarantee you'll be disappointed with the upstairs. A HUGE portion of the summer heat load will be upstairs. The odds of your current ducts sending enough air up there in the summer is slim to none. If they did the upstairs would be scorching hot in the winter compared to downstairs. So you'll need to upgrade the upstairs ducts to get enough air up there in the summer. And you'll need some sort of zone control (manual or automated dampers) to adjust that back down for the winter. Check the sig links for more.

Make sure they perform a proper heat load calculation. Not that the tech suggested otherwise, but "probably 4 ton" is a bad way to surmise the heat load. MANY homes your size could easily be cooled by something smaller.

Don't know where you are located but I would say unless you are living in a glass house 4 tons is way oversize. I would have grave concerns about the ductwork in a 1800 sq. ft. house being able to handle 1600 cfm of air. Make sure your supplier is doing a heat loss to get the correct size. Even with the worst "rule of thumb" guess you would not be above 2.5 tons.